Higher animals including man each carry approximately 100,000 genes, but only about 15% thereof is expressed, and characteristics of individual's biological process, e.g., genesis, differentiation, homeostasis, responses to stimuli, control of cell segmentation, aging and apoptosis(programmed cell death), are determined depending on which genes are expressed(see Liang, P. and A. B. Pardee, Science, 257: 967-971(1992)).
Pathogenic phenomena such as tumorigenesis are caused by gene mutation which brings about changes in the mode of gene expression. Therefore, comparative studies of gene expressions in various cells have been conducted to provide bases for establishing viable approaches to the understanding of diverse biological phenomena.
For example, the mRNA differential display(DD) method suggested by Liang and Pardee is effective in elucidating the nature of tumor suppressor genes, cell cycle-related genes and transcriptional regulatory genes that control apoptosis(see Liang, P. and A. B. Pardee supra). Further, the DD method has been widely used in examining the interrelationship of various genes in a cell.
It has been reported that tumorigenesis is caused by various genetic changes such as the loss of chromosomal heterozygosity, activation of oncogenes and inactivation of tumor suppressor genes, e.g., p53 gene(see Bishop, J. M., Cell, 64: 235-248(1991); and Hunter, T., Cell, 64: 249-270(1991)). Further, it has been reported that 10 to 30% of human cancer arises from the activation of oncogene through amplification of protooncogenes.
Therefore, the activation of protooncogenes plays an important role in the etiology of many tumors and there has existed a need to identify protooncogenes.
The present inventor has endeavored to unravel examine the mechanism involved in the tumorigenesis of cervical cancer; and, has unexpectedly found that a novel protooncogene, human cervical cancer 2(HCCR-2), is specifically overexpressed in cancer cells. This protooncogene can be effectively used in diagnosis, prevention and treatment of various cancers, e.g., leukemia, lymphoma, colon, breast, kidney, stomach, lung, ovary and uterine cervix cancers.